Recently, impact-absorbing members have been developed especially for automotive interiors and exteriors from a viewpoint of protection of pedestrians and passengers. Also, for containers used in mechanical systems, electrical systems or the like, impact-absorbing members have been developed for containers to protect persons and contents in case of collision, impact or drop. These conventional impact-absorbing members are mostly made of metal although the metal is recently being replaced by lightweight resin. The impact-absorbing member constituting a part of a structure is required to have stiffness enough to suppress deformation caused by impact, as well as a sufficient impact-absorption. Therefore it could be helpful to provide a material capable of absorbing external impact energy with less deformation. To meet such required specifications, a formed body made of fiber-reinforced resin composition or another formed body made of non-reinforced resin composition may be used as a resinous impact-absorbing member.
For example of the formed body made of fiber-reinforced resin composition, JP 2006-083227-A discloses an exterior formed body having non-reinforced polyamide resin layers disposed on both sides of a long fiber-reinforced polyamide resin layer in which a layer thickness ratio of [long fiber-reinforced resin layer/non-reinforced resin layer] is 1.0 or higher. JP 2002-283522-A discloses a multilayer injection-molded body having skin layers and a core layer, the skin layer being made of a composition of polyamide and olefin-based elastomer, the core layer being made of another composition of polyamide and a reinforcing filling material. However, such formed bodies as disclosed in those publications cannot meet the requirements of impact-absorbing members because the formed body of the fiber-reinforced resin composition absorbs impact energy as fracturing, so that a container made of the formed body might have leakage of fluid content and that external impact energy applied might spread sharp-edge fractions from the formed body in sharp-edge fracture morphology.
On the other hand, for example, of the non-reinforced resin composition, JP 2009-155365-A discloses an impact-absorbing member, which has a rib structure of 50% or more height of thickness of a plain portion and is made of thermoplastic resin composition comprising a thermoplastic resin and a resin having a reactive functional group. However, such a member as shown in those publications might deform greatly when external impact energy is applied. Particularly under the environment where deformation is restricted, it is difficult for the member to sufficiently absorb the impact energy and therefore to be provided as an impact-absorbing member.
It could therefore be helpful to provide an impact-absorbing member capable of absorbing external impact energy with less deformation.